Reflector



1963 w. F. CROSBY ETAL 3,112,893

REFLECTOR.

Filed Aug. 11, 1961 INVENTORS h/uunn EC/eosBY mm 0/)RYL 0. JqLL/vA/vUnited States Patent 3,Til2,$93 REFLECTUR William F. Eroshy, NewBerliord, Mesa, and Daryl D. Sullivan, Corning, FLY, assignors toCorning Glass Works, (learning, N.Y., a corporation of New York FiledAug. ll, N61, fler. No. 13%,663 Claims. (ill. 24ll-ltl3) This inventionrelates to optical reflectors and more particularly to a novel reflectorwhich is mountable in and conformable to the general shapes of presentlyexisting luminaire housings of varying designs but which exhibitsoptical advantages characteristic of reflectors having circular crosssections.

Presently existing luminaire housings exist in a variety of shapesdictated by such considerations as appearance, available space and theamount of light which is to be emitted in any given direction. Onedisadvantage encountered in luminaires having non-spherical reflectorsis the fact that light traveling from the reflector to any point on therefractor does not impinge on the refractor at the same angle as lightrays traveling from the light center directly to the same point.Consequently, it is diflicult to design refractors which, when used inconjunction with non-spherical reflectors, will transmit both directrays and reflected rays in the directions necessary to given desiredpatterns of illumination. This difficulty is encountered to a muchlesser degree in luminaires employing reflectors which are circular incross section, since such reflectors redirect light rays such that theircomponents in the planes of the circular sections are coincident withthose of rays traveling directly from the light center to the samepoints on the refractor.

Accordingly, it is an object of this invention to provide a reflectorwhich can be conveniently substituted for the reflectors in presentlyexisting luminaires and which exhibits the above-mentionedcharacteristics generally found only in reflectors having circular crosssections.

This and other obiects which will be apparent from the followingdescription are accomplished by the provision of a reflector having astepped reflecting surface which comprises a plurality of surfaces ofrevolution about a common directrix, said surfaces intersecting at leastone plane perpendicular to the directrix so as to form circles ofdiffering radii about the point of intersection of the plane and thedirectrix.

The construction and functioning of the reflector of this invention canbe understood by a reference to the accompanying drawing representingone embodiment suitable for inclusion in a generally ovate luminaire,wherein:

FIGURE 1 is a plan view looking into the reflector of this invention,

FIGURE 2 is a view taken on line 2-2 of FIGURE 1,

FIGURE 3 is a view taken on line 3-3 of FIGURE 1, and

FIGURE 4 is a typical sectional View of the reflector taken as indicatedby line i -4 of FIGURE 2.

As previously pointed out, the reflecting surface of the reflector ofthis invention comprises a plurality of surfaces of revolution. Atypical arrangement is illustrated in the drawing in the form ofreflector it) having a generally ovate shape, as indicated by ovalreflector rim ll, and having a reflecting surface 12 which is generallyovate in shape but which is made up of re ecting steps, such as 13,which are in the form of surfaces of revolution with a common directrixpassing through light center 14 perpendicular to the plane of the paperin FIGURES 1 and 4 and indicated by broken line 16 in FIGURES 2 and 3.

It is a characteristic of a surface of revolution that its intersectionwith planes perpendicular to its directrix are in the form of arcs ofcircles having their centers at the hllzfiflfi PatentecliDec. 3, i965"ice intersections of the directrix with the respective planes. Atypical curve 15 formed by the intersection of surface 12 of reflectorlit with the plane perpendicular to the directrix of its steppedsurfaces is indicated in FZGURE 4 and is representative of theintersection of any such plane with the reflector surface. As can beseen, this intersection is in the form of a number of arcs of concentriccircles having their center on directrix 16. These arcs are connected bylines such as 17, which preferably lie in a radial direction withrespect to the center of curvature of the arcs so that substantially nolight is reflected therefrom. That is, the surfaces, such as 18, whichform the loci of lines 17 and which connect the circular steps 13, liein planes which pass through and include directrix 16. It is to beunderstood that any plane perpendicular to directrix 16 will intersectsurface 12 to form a curve generally similar to curve 15.

Since any plane perpendicular to directrix it? will intersect thereflector in a series of circles, and since, as can be seen from thedrawings, all light emitted from light center 14 and impinging onreflector surface 12 falls upon the steps 13 which consist of the lociof these circles, it follows that all such light will fail upon somesuch imaginary circular intersection. Any light ray falling upon anysuch imaginary circular intersection may be considered as having twocomponents, one in the plane of the intersection and the other in adirection perpendicular to this plane and parallel to the directrix.According to well-known optical laws, the component in the plane will bereflected from the circular intersection back in the same path which itfollowed in reaching the circular intersection and through the pointforming the intersection of the directrix with the plane of the circularintersection. Since the only other component lies parallel to thedirectriX, it is seen that the path of the actual reflected ray willdififer from this reflected component only by the addition of acomponent parallel tot he directrix. That is, the actual reflected raywill also pass through some point along the directrix. Thus all raysemitted from light center 14 and impinging on the surface of reflectorit) will be directed back through directrix 16.

All rays emitted from light center 14 and reflected through directrix 16fall either on the reflector or on the refractor. If a ray falls on thereflector, it will once again be redirected through the directrix and sorepeatedly until it finally emerges from the reflector to impinge on therefractor. This means that all rays impinging on the refractor will comefrom the direction of some point on the directrix. That is, all raysimpinging on any given point on the refractor lie in a plane passingthrough that point and including directrix lie and hence have the samecomponents in a plane which passes through that point on the refractorand is perpendicular to the directrix.

Thus, if, for example, reflector ltl is included in a street lightinglurninaire, directrix 16 might be oriented vertically, and all raysfalling on any point on the refractor would have the same components inthe horizontal direction. Consequently, the problem of redirecting inhorizontal directions the light emitted from the luminaire issimplified, since the refractor will bend through the same angle in thehorizontal plane and emit in the same horizontal direction bothreflected rays and those passing directly from the light center to therefractor. Such luminaires are of particular value where accuratehorizontal light distribution is necessary, as, for example, in fourwayluminaires for lighting street intersections and for directing beams oflight down both streets in each direction.

Although the reflector of this invention has been illustrated in anembodiment suitable for inclusion in an ovate luminaire housing, itshould be understood that the various surfaces of revolution comprisingthe reflecting surfaces thereof may be formed with varying radii to giveany desired overall confl uration to the reflector while retaining itscharacteristic optical circularity.

What is claimed is:

1. A reflector having a concave reflecting surface with an edge definingan opening for the emission of light from said reflector, saidreflecting surface comprising a plurality of surfaces of revolutionabout a common directrix passing through said opening, said surfaces ofrevolution intersecting at least one plane perpendicular to saiddirectrix so as to form a plurality of arcs of circles having differingradii and having a common center at the intersection of said directrixwith said plane perpendicular thereto, said arcs forming together agenerally non-circular configuration.

2. A reflector according to claim 1 wherein said reflecting surfaces areconnected by surfaces lying in planes which include said directrix.

3. In a concave reflector of generally ovate form having an edgedefining an opening for the emission of light from said reflector, theimprovement which comprises forming the inner surface of said reflectoras a series of surfaces of revolution about a common directrix passingthrough said opening, at least two of said surfaces of revolutionintersecting a plane perpendicular to said directrix to form circles ofdiffering radii and having a common center at the intersection of saiddirectrix and said plane perpendicular thereto, said arcs formingtogether a generally non-circular configuration.

4. A reflector according to claim 3 in which said sur- '4 faces ofrevolution are connected by surfaces lying in planes which include saiddirectrix.

5. The combination with the light source of a reflector having a concavereflecting surface with an edge defining an opening for the emission oflight from said reflector, said reflector having a continuous innersurface comprising a plurality of steps, each of said steps comprising asurface of revolution and a plane surface, each of said surfaces ofrevolution having a common directrix passing through said light sourceand said opening and each of said plane surfaces being in a plane whichpasses through and includes said directrix, said steps being formed suchthat the said surface of revolution of each step connects with the saidplane surface of another step, said surfaces of revolution intersectingat least one plane perpendicular to said directrix so as to form aplurality of arcs of circles having differing radii and a common centerat the intersection of said directrix and said plane perpendicularthereto.

References Cited in the file of this patent UNITED STATES PATENTS1,189,621 Post et al. July 4, 1916 1,814,326 Melton July 14, 19312,196,548 Cohu Apr. 9, 1940 FOREIGN PATENTS 475,410 Great Britain Nov.16, 1937 533,135 Belgium Nov. 30, 1954

1. A REFLECTOR HAVING A CONCAVE REFLECTING SURFACE WITH AN EDGE DEFINING AN OPENING FOR THE EMISSION OF LIGHT FROM SAID REFLECTOR, SAID REFLECTING SURFACE COMPRISING A PLURALITY OF SURFACES OF REVOLUTION ABOUT A COMMON DIRECTRIX PASSING THROUGH SAID OPENING, SAID SURFACES OF REVOLUTION INTERSECTING AT LEAST ONE PLANE PERPENDICULAR TO SAID DIRECTRIX SO AS TO FORM A PLURALITY OF ARCS OF CIRCLES HAVING DIFFERING RADII AND HAVING A COMMON CENTER AT THE INTERSECTION OF SAID DIRECTRIX WITH SAID PLANE PERPENDICULAR THERETO, SAID ARCS FORMING TOGETHER A GENERALLY NON-CIRCULAR CONFIGURATION. 